value of X=0 from if statement is not plotting in matlab graph

Trying to plot a graph for ask, fsk & psk modulation from binary input. The graphs of psk and fsk modulation are ok, but the ask modulation graph seems to ignore the 0 values and doesn't plot them.

tried using ask=sin(0); ask=stairs(0); and reversing the if else statement

prompt = 'Enter bit stream ';
ff = 'Enter space frequency, f = ';
ff2 = 'Enter mark frequency, f2 = ';

x=input(prompt)
f=input(ff)
f2=input(ff2)
nx=size(x,2);

for i=1:1:nx
 t = i:0.01:i+1;
if x(i)==1
   ask=sin(2*pi*f*t);
   fsk=sin(2*pi*f2*t);
   psk=sin(2*pi*f*t);
else
    ask=0;
    fsk=sin(2*pi*f*t);
    psk=sin(2*pi*f*t+pi);
end

subplot(4,1,1);
stairs([x,x(end)]);
hold on;
grid on;
ylabel('Amplitude')
xlabel('Time')
title('Binary Input')
axis([1 nx+3 -2 2]);

subplot(4,1,2);
plot(t,ask);
hold on;
grid on;
ylabel('Amplitude')
xlabel('Time')
title('ASK Modulation')
axis([1 nx+3 -2 2]);

subplot(4,1,3);
plot(t,fsk);
hold on;
grid on;
ylabel('Amplitude')
xlabel('Time')
title('FSK Modulation')
axis([1 nx+3 -2 2]);

subplot(4,1,4);
plot(t,psk);
hold on;
grid on;
ylabel('Amplitude')
xlabel('Time')
title('PSK Modulation')
axis([1 nx+3 -2 2]);

end

Here's the current output

Solution

Whenever plotting in matlab your data need to be the same length. In your case, you're trying to plot a single 0 over your entire t vector for ask. You need to change this to a zeros vector, like this:

prompt = 'Enter bit stream ';
ff = 'Enter space frequency, f = ';
ff2 = 'Enter mark frequency, f2 = ';

x=input(prompt)
f=input(ff)
f2=input(ff2)
nx=size(x,2);

for i=1:1:nx
    t = i:0.01:i+1;
    if x(i)==1
        ask=sin(2*pi*f*t);
        fsk=sin(2*pi*f2*t);
        psk=sin(2*pi*f*t);
    else
        ask=zeros(length(t), 1);
        fsk=sin(2*pi*f*t);
        psk=sin(2*pi*f*t+pi);
    end

    subplot(4,1,1);
    stairs([x,x(end)]);
    hold on;
    grid on;
    ylabel('Amplitude')
    xlabel('Time')
    title('Binary Input')
    axis([1 nx+3 -2 2]);

    subplot(4,1,2);
    plot(t,ask);
    hold on;
    grid on;
    ylabel('Amplitude')
    xlabel('Time')
    title('ASK Modulation')
    axis([1 nx+3 -2 2]);

    subplot(4,1,3);
    plot(t,fsk);
    hold on;
    grid on;
    ylabel('Amplitude')
    xlabel('Time')
    title('FSK Modulation')
    axis([1 nx+3 -2 2]);

    subplot(4,1,4);
    plot(t,psk);
    hold on;
    grid on;
    ylabel('Amplitude')
    xlabel('Time')
    title('PSK Modulation')
    axis([1 nx+3 -2 2]);

end

Now you get something like this: